Magento 2 add custom rest api endpoints
{base_url}/rest/default/V1/mma/categories
{base_url}/rest/default/V1/mma/braintree/token
{base_url}/rest/default/V1/mma/me/vault/items
{base_url}/rest/default/V1/mma/me/vault/nonce
{base_url}/rest/default/V1/mma/paypal/transparent/securityToken/:quote_id
{base_url}/rest/default/V1/mma/magento/version
{base_url}/rest/default/V1/mma/products/most-viewed/:limit
{base_url}/rest/default/V1/mma/products/best-seller/:limit
{base_url}/rest/default/V1/mma/products/top-rated/:limit
{base_url}/rest/default/V1/mma/products/new/:limit
{base_url}/rest/default/V1/mma/review/reviews/:productId
{base_url}/rest/default/V1/mma/rating/ratings/:store_id
{base_url}/rest/default/V1/mma/review/mine/post
{base_url}/rest/default/V1/mma/review/guest/post
{base_url}/rest/default/V1/mma/contact/post
composer require mma/customapi
php bin/magento setup:upgrade
php bin/magento cache:clean
Tested on Magento Commerce 2.2.5
Check my videos about Magento 2 Rest API development basics https://www.youtube.com/playlist?list=PL97fL9DAn9Qy5kCQfPVrfh9pGNYeG0vmS